Toll switchboard



May 8, 1956 H. REAGAN TOLL SWITCHBOARD 7 Sheets-Sheet 1 Filed Jan. 16,1953 N u R |II m n Y R Il l E m @E m @I m mi Ol ilo w H. 1 w v 6E NGE EN. @Ti 252:0 h l L Qou Tl D EIS Ew QE: THIY N IHO m1 w`\ w .QE m \v E@ommo l di mmmw mmazmm 35@ @T1 IMHwJOM 121D ZOPWOQ t\ 9\ O`N mON msi VIIlmSom @-lwmmwL vdl m @mou l||\| Qlmzornmd mama o-\ Noma 62.

ATTORNEY May 8, 1956 l., H. REAGAN TOLL SWITCHBOARD 7 Sheets-Sheet 2Filed Jan. 16, 1953 N .mi @mou tu .ht

L; INVENTOR.

v LEON H. REAGAN Bym ATTORNEY MON! EN! JOQFZOO tobxtmlo vNN mON q OONQCMN ONN 9N NONX May 8, 1956 l.. H. REAGAN 2,744,964

TOLL SWITCHBOARD med Jan. 1e, 195s 7 sheets-sheet s INVENTOR. LEON H.REAGAN ATTORNEY May 8, 1956 L. H. REAGAN TOLL SWITCHBOARD 7 Sheets-Sheet4 Filed Jan. 16, 1953 May 8, 1956 l.. H. REAGAN Tou. swITcHBoARD 7Sheets-Sheet 5 Filed Jan. 16, 1953` N A m. Y R. A E w E M m R. m .DUIZOCLwOl m H T N A O E lv II- SETL 2 L ,.5528 @Y E8 .Guion nog nzm wom;3L N .ESI Gudo hZOtl QZDLmt omm l.. H. REAGAN 2,744,964

7 Sheets-Sheet 6 @E tm wommo TOLL SWITCHBOARD May s, 195e Filed Jan. 16,19.53

L. H. REAGAN TOLL SWITCHBOARD May s, 195e Filed Jan. 16, 1953 '7Sheets-Sheet '7 #Sota QIOO @200mm N .u Y @Tm me M m M N H n I N A O u Bmy? fcx /momx L-, il o4 il .5528 .5528 /|||J\||||\ ommmo pmmo wd Ffm; ovom om o m United States Patent'I Otiice 2,744,964 Patented May 8 l19,56

TOLL- swrr'cnno'xnn Leon H. Reagan,.-Richland, .Wash.,tsassgnor, bymesne assignments, to General Dynamics Corporatioma corporation of.Delaware fApplicationJanuary 16, 1953,Serial No. 331,627

17. claims. V(c1. .17a-'27) This inventionfrelates to anelectro-mechanical tele- -4`phone system 'and more specifically lto'anoperators--toll --board. 'Thislinvention is'adapted lto cooperate withakeyvsender of "type 4shown -in my ycopendingI application 'SerialiNumber 311,845', tiled September 27,'"l952ynovv Patent 2,730,568, boththis and the subjectapplicationI being asy:signed lto the same assignee.

Electro-mechanical telephone systems, as` theyra're I "known today,often require both -a human `operator'and a`pluralityrof directivelycontrolled switches toz `extend ay connection'from a calling line toaicalled lir1e.""'In such asystem, the calling subscriber inititates acall and lihis line lis extended to an operator position `by"any'suitable ineans.` fFor example, :he `may be on vardirect linetermi--nating at a switchboard jack or there may be directively 'controlledswitches 'wherein a particular digit zero lfor '-example, is dialed toseize :an operator.

The operator may answer the ycall by anysuitable 'equipment such asa'plug andl jack, cord circuit, position circuit, land the like;IlUsually the operatormhas apln- 'rality of cord circuits; any'one ofywhichmay 'bemade individual kto a particular fcall. cuits are commontofall of they cord circuits; therefore,

A secondA 'group ofjcirwhen she lanswers the call, it islnecessary"for'herto associate this ;common -equipmentfwith thep'arfti'cularcord circuit that is individual to the call.`lI'iollowinglthisgthe *operator transmitsswitch directingl signals 'overthe 'calling'or frontplug of her cord circuit vfor setting :suitable'telephone-equipment to seize a called subscriber. She VAmay use'eithera key vsender -or a dial totransmit these signals.

l Systems of this type are subject to many undesirable features vwhichhavel'come to be accepted as characteristic or-inher'ent to the-equipment which must be used :For example, during the various stagesthrough'which aftelephone 'callzp'rogresses,the circuit is subjecttounba'lances, sparking or-'the like, thereby creating unduenoise .inthe *operator-s headset." This vis both fatiguingand annoying.

In-"the-fpastya-n operator `had to A'perform Acertaintun'cvtions in -alcertain sequence; for "example, she 'could not return llher talk key tonormal -until thecompletion of all `of her operations. This'reducesoperatorex'ib'ility.

Furthermore, an operator has vnot been providedfwith .an' `option forpositively' preventing while Still permitting the interconnectionl ofconversation paths `in the operators circuiti This invention, on the"other hand, is arranged to positively'prevent the interconnection oftwo cords lwhile providing an`operator option for 4overriding Athis""preventionmeans thereby interconnecting cord circuits.

' One object of this invention is to 'provide a newand 'improvedftoolswitchboard.

A secondobject of this invention is to eliminate or reduce extraneous"noises occurring in the-'operators lheadf iset.

Anotherobject of this invention is to Iincrease'the ef- --1'iciencyofthe #operators-headset by providing proper fantisi'detone balancevatall times-without regard as to 'whether a circuit -ispluggedintoaltrunk or not.

r:laid out to -pr-.ovide .ay complete :and..operable. circuit Stillanother Yobject of this invention is to provide a positive Tinterlockwhereby the operator is Apreventedtrom ...interconnecting twoconversation circuits.

A .turtherobject .of this invention isprovidingmeans for. giving.the,operator,an option permitting .thai-utert .connection of twocircuitsV upon the performanceA oflcertain .definite acts.

A .still further object of this invention :is in. provid1ng.increased'-voperator flexibility by.. reducing .thenumbenof operationswhich must be performed ina given sequence.

Yet .anotherobject is to prevent .the simultaneousasso- *.ciationnoisthedial. circuitwith two or -mor. :.cordA circuits.

. These:.and still other. objects will. be'more .apparent yby .makingreference to the .accompanying drawing .in whiych:

vFig. -1 shows .ablock diagram of how .the-.remaining .guresinterconnect to form a telephone system.

Fig. .2 .shows .a cord circuit. l .Figs 3 and 5, when properly joined,illustrate 4.a ...position circuit.

-EigA gives details of a vdial circuit.

f .'Fig. v6 is .anoperator circuit.

.' Fig. 7 shows the manner inwhich Figs. .2-6should'lbe Fig. 8illustrates the manner in which two cord-scircuits areprevented..from.kseizingeommon equipment simultaneously.

f Ther.:circu`its of- Figs. 2-6 and z8V illustrate' the battery vconnectionsbyy conventional :symbols:` As i'stthesca'serfin .mostAtelephone circuits;7 the :tpositiveftermnal'f'isndescribed.assconnectedwithwgronnd For dhis'f're'ason, I

`refer `tothe negative pole` as (-)battery `and the positive .-.pole asrgrounded my invention. f f

Fig. -1 :schematically .illustrates theequipmentrwhichfis shown .indetail in yFigs. 2-6.- Inwthisfgure vit is .ias- :surnedthat a callingparty A seizes ianzoperxsttors.posi- -.'tion,1for example at ljack 1201,by. anvrsuitableltelephone vequipment A209, .responsive to which anoperator'tinter- "connectsqplug P202 and'. jack J201 'thereby.makingwlthe talk key, a circuit maybe completed'over cablei 1125. by

which lthe operator-circuit inl Fig. 6 is :conditioned to 'extenda'talking path tothe operators .headsetf16, vUpon conversing withcalling party A, y the l:operatorlearns-the `destination of the call`which `isfassumeclto beftot sub- .scriber C. Following Lthis, she'mayeitherf'use .a dialt in Fig. 4 ora registers sender 17 Efor extendingVswitclrcorntrol signals over cable10', through the lcord circuitandiplug P208 to automaticA equipment A210,.wheresconventional equipmentis set to seizecalled subscriber 4C. fr

It is though `that a more 'complete understanding -of this .invention.is 'facilitated .by `a detailedwdescriptionbf Figs. 2-6...Theseztigures titogetherfiname mannensh'own f in Fig. i7 andncorrespond to the showing 'of tFig. '1. HFor example, cableY 10 isshown Anearthe lower right of Fig. 12, `cables 12 and 13 are shown inFig. '5, cable 'l1-interconnects Figs. 4 and 6, via Fig. 5, 'cable'18'extends'lfrom the operator circuit to her headset which isshownenear-lthe Yright centerv of Fig. 6, cable 14 is shown in Ljl-ig.it as extending to theregister sender, cable' 15 also fconnects with-thevkey `circuit and it is shown near 'the flower ,right lportion of Fig.6. As tothe register,"sender an'dkey- V"set, "reference is made vtoymyc/copen'ding'application,

It shouldr be'understood -zthat nthis' condition couldbe reversedA or.that any'other wells-known power source may be usedwvithoutuchanging atthis time.

Serial Number 311,845, led September 27, 1952, now

' Patent 2,730,568, for a complete disclosure of such equipment.

' Operator takes position The operators circuit, Fig. 6, is common tomany cord circuits and is adapted to complete the talking paths fromoperators headset 16 to either calling subscriber A or called subscriberC. However, before the operator can converse with any subscribers, shemust take position r stated otherwise, she must prepare the talking pathof Fig. 6. First, plug P605 is connected with jack 1604,

thereby completing a talking path between her headset 16 and inductioncoil R603 via cable 18. Responsive thereto, operator battery relay 640operates from battery through the winding of relay 640, cable 18 throughthe transmitter portion of operators headset 16 and back over cable 18through the winding of retard coil 660 j to a grounded `battery toheadset 16. Operator battery relay 640 closes This circuit alsofurnishes talking contact 642 and completes a marking over thePTconductor to a position take relay in the register control circuit of`akey sender is provided. Relay 640 also closes contacts 644 to extend asignal tothe chief:` operators desk indicative of the fact that theoperator has taken position. The receiver portion of operators headset16 is now connected over cable 18 and through contacts 631 and633 to thesecondary winding of inductance coil Operator answers call .Toillustrate the invention, a typical call will be described.` It isassumed that subscriber A is calling subvice such as talk key K202 isnecessary for making the cord circuit individual to the commonequipment.

The operator must now associate her common equip- -ment with the cordcircuit of Fig. 2. To do this, she operates talk key K202 therebycompleting a circuit to operaotr control relay 220 which operates overthe circuit from grounded (-1-) through the winding of relay 220,operated contacts K203, conductor O, contacts 322 to battery B301 by wayof contacts 313 and resistor R302. Operator control relay 220 operateshalf V way due to the resistance characteristics selected for elementR302 to close its preliminary or X contacts 222, thereby completing acircuit for fully energizing relay 220 in series with master relay 310,the circuit being traced from battery to the lower winding of operatorcontrol relay 220, contacts 222, operated con- Vtacts K204, the Hconductor and through the windings of-master relay 310 to grounded(-1-). Relay 310 operates to prepare the operators circuit as will beexplained later. It also completes a circuit for a second master relay320 which operates but has no function Contacts 221 complete a signalpath from the kcysendcr to' Switching relay 410 if dual sender circuitsare used. At contacts 223 and 225', operator control relay 220 breakscontact between rear ring and tip v conductors RR and RT and front ringand tip conductors FR and FT; instead, a circuit is completed by way ofcontacts l222 from rear ring conductor RR to operators rear ringconductor ORR and at contacts 226' to operators rear tip conductor ORT.At contacts 224 and 227 a connection is completed'between the front lwhich supervision usually is extended. This is so that the sleeveconductors may be used to control the opera- 4 tion of certain circuits.For example, rear sleeve lead RS is disconnected from rear lamp lead RLat contact 226 while a similar front connection is broken at contact228. Meanwhile, a circuit is completed at contacts 227 for operatingrear sleeve relay 360. This circuit may be traced from plug P200 overrear sleeve conductor RS, through contacts 227 over conductor RSI andthrough relays 350 and 360 to battery. Relay 360 operates contacts 361which energizes relay 370. The resistors around the windings of relays370 and 380 provide for spark suppression.

In a similar manner, contacts 228 open to disconnect supervisory lampL217 from front sleeve FS. Contacts 221 close a circuit for operatingfront sleeve relay 340 which in turn closes its contacts 341 foroperating a second front sleeve relay 380.

An anti-sidetone balance is maintained in the operators headset at alltimes. For example, before the operator may converse with the callingparty, it is necessary to prepare the operators circuit includingvarious switching operations in the talking path and therefore it isnecessary to switch terminations into and out of the circuit. For thispurpose, master relay 310 operated in series with operator control relay220 thereby closing contacts 314 to extend battery B301 overconductorTR, contacts K503, and conductor TO to pull operatortermination relay 620. This relay opens contacts 622 thereby removingterminating resistance R605 from across conductors T and R. Thisresistance is utilized to provide a proper anti-sidetone balance in theoperators headset. At contacts 62'1, relay 620 also connects the MG andA leads together for forwarding a signal in the form of a ground markingfrom dial front keyrK401 to the EK lead via contacts K402a, K408q,conductor MG, contacts 621, conductors A and EK as a start signal to thekey sender if one is provided. This same ground marking is placed onconductor KO via contacts 431 to signal the register controller circuit.A conversation circuit is now complete between the operators headset andthe calling subscriber so that the destination of the call may bedetermined. This conversation circuit may be traced as follows: Fromplug P200 over contacts K205 of ring rear key K207, conductor RR,contacts 216 and 222', conductor ORR, operated contacts 373, conductorORR and on to the operators circuit by Way of contacts on the refundrear, collect rear, and talk front keys. In the operators circuit, theconversation path is completed to the operators headset via conductor R,capacitor C602, contacts 635, induction coil R603, jack 1604 and plugP605. The talking circuit returns to plug P200 over conductors parallelto the path just traced.

The operator speaks with the calling party and determines the directorynumber of the called party after which she inserts plug P208 into jack1209 and otherwise prepares to dial the called number. First, it isnecessary to associate the dial circuit (Fig. 4) with the front cordattached to plug P208. For this purpose, dial front keyK401 is operatedto place a grounded (-1-) marking onconductor PUC, which extends fromcontacts K402 through contacts 452 and the winding of pick-up relay 440to battery. This pick-up `relay operates and locks to conductor PUC atcontacts 442. Contacts 444 close to complete a path between conductor ONand battery by way of resistor R410. This prepares the trunk circuit fordialing over the circuit which will .be from battery through resistorR410, contacts 444, conductor ON, contacts 424, 415, and 237 to fronttip FT, contacts ofthe ring front key, plug P208 and jack 1209 to thetrunk circuit in automatic equipment A210. Contacts 443 close therebyextending grounded over conductor SW, contacts 451, and throughthe lowerwinding of switching relay 420 which operates to interconnect the dialand cord circuits. Contacts 443 also` cause the operation of dial relay460 and prepare a locking path for `completed by way Jaw-45o.

together with pick-up relay 440 completes a circuit to.

place a grounded marking on conductor PUF for .connecting the frontcordcircuit ,to/'extend `dial pulses xfrom-the dial circuit Ito-.switch-train;A210./= This mark- Z :ing may. be .traced from .groundedonfcontacts V443 andv to .conductor SW, contacts,f451 and.contacter-425, rpick-up conductor-PU; operated contacts `K403 tofcon--ductorPUF which continuesto` the-.cord circuit. and dirough operatedcontacts 223 to operate `dial f front ,reslay 230.. '..TheresistancefaroundI relay 230prevents damage ,by suppressing possiblesparking. Relay 230 closescontacts 235 :thereby extending .fronti ringconductor FR to .pulsing conductor PL while ycontacts. 237 connectlfront vtip to' off-normalconductor ON.-.-1Dia1 -front vrelay :,230completes a circuit `for returning the vgroundedt-.j-U

`marking on conductor PUE tothe `dial-.circuit.bycon :tactsr'451'thereby/"removing 'the Voriginal marking ground @which was extended overconductor PUF; howevendial front relay 230 1 continues to holdsince'contacts454 close a'circuit from conductor H1 to grounded ('-i-)byWayY of contacts 463. It-might betnoted L'that contacts 5454' 'are' Xcontacts vwhich close vbefore other vcontacts 35 V-openthus insuringfthereturn of Agrounded on conf ductor HI before the removal of ``groundedon conductor PUF. Relay 450-opens contacts --452'which isin theoriginaloperating circuit -for pick-up 'relay 440; v-howfever, relay 440 lisheldoperated by'way ofits owni'confvv 40 v 'tacts '442 :andconductor PUCwhich Vleadsy to `a grounded 1-(`1{) cooperated contactslK402.-` A`locking circuit is of contacts 463 and'454 to hold -re- E i Toreview'brieily, it 'maybe recalled that dial-'front 'rrlay 230 .is nowoperated,v the dial 'circuit is' individual to the cord circuit Iand isholding thereto'under--the 'in- 'signal .and lhang for :a rshortinterval. During' Xthat interval, the operator may return talk key X202tofnorf 'mal.`. This means lthat the rear'cord circuit-Would apl""lJearas '.open*` :and 'howl unless some sort' of` ani-idle `zlineterminationis provided.' To avoidrsuch'an open condition, dial front relay 230closes its contacts 233^and 234 therebyplacing :an idle 1ineterminationon the` rear cord. This termination may b'e'traced'from 'the rear ringA'conductor 1RR`through :contacts 216, i223'v "and 1234,

i capacitor-resistancenetworkN209, contacts 233,.225"..and

Il17zto the rear tip` conductor RT. Itwshouldmbenoted -that in lease-theoperator returns 4thetalkl 1key to normal, yrelay.220 releases andtherefore contacts 223' and..225' .are closed. In case` the voperatorhas not returnedtalk key-K202 to `normal at v.this .time,network N209isfstill .-,placed across the rear cord; although the termination isy.not necessary. This time-thepath maybe .traced from .network .N209over contacts 233 and 234, 2241and. 227',

f' `conductors OFR and OFT, contacts 383 and. 3.85, :contacts of refundand collect .front keys,v talkrearrandt-,talk .front keys, refund andvvcollect rear --keys,contacts 373 3,75, conductors ORR .fand ORT,ycontacts 222'. and 226.',216 and 217 tothe rear cord. 4 u l.

thefcircuitssare now in condition, ,for `the trans-`rmission..oi..switch controlling signals, yit is necessary rto .notify:theI operator that -she .may key ordial the called partysf number;Vhence .a. circuit is -closed for lighting 5 .start-stop lamps L403.Thisr Ycircuit vmay be traced fromI `grounded (fl-) through contacts316, 331, .conductor.FL1, .contacts 229,232, the SR conductor,-contact`s=1t411I and426 tobattery by way of start-stop lamp.L403-Which` lights.

i. Itlshould `benoted that a. grounded (+)marking isnow eXtendedbyway ofcontacts K408 on `the wipe-out keyfdialaimpulsing contacts K40f7 and the.pulsing connductorlL, .through operated.- contacts 422, rest contacts413.@andoperated contacts 235 to the frontring con- `ductor FR.

, v Operator dials The' operator may Vmove the dial Aoflfnorinalpreparaxtoryl to transmitting 'the' first digit indication of the'called Xpart'ysnumber.A In'doing so, lshe closes contacts K405 whichextends a grounded marking over the"otnormahfconduc'torONl throughcontacts462A and the wind- -ing of'oifnormakrelay470"to(-) battery. Therey --s'istance"arourrdrelayy 470 4'is for spark protection.Conyft`acts472 "close a circuitfor extending a battery marking'fby'wayo'f 'resistance R410 to off-normal co'nductor '0N i'nfparajllel withcontacts 444. This is'Kbe- "causerelay 440 may release before thebattery should Y'be r'e'moyed =in"some"cases. Off-normal relay'470 also;"closes japair of locking paths for itself one ofwhich is "by way ofitscontacts' 473 and contacts' 443 and the 4r'otherofwhich `is'byway ofcontacts 471,`conductor' ON1 -`and'contactsv'K405. i 7"The"operatorreleasesthe `dial and it 'returns to normal `1tran-srriittingsuitableswitch.` controlling .signals in accordlanc'ewith the `dialset-tirlg.For example, in returning .to Lnormal,-co1`1tacts K407 yopen-.andclosealternately break ling and closing `the pulsing 'path extendingfrom grounded by way'of contacts K408 and K407 to the PL V "conductorand hence to frontringconductor FR. There- "f0re,a"train` of outgoingground pulses is transmitted over "feonductoriFR, plug :P208 and ljack1209 for, operating a suitable` svvitch"tra'in` in automatic switchingequipvv"merit A210. Subsequent digit indications maybetransimittedsimilarlyintothe switch train of A210for seizing calledfsubscriber C.

Restonaton of circuits after dialing i Afterthe operator hasl dialed thelast digit, she ref'stores dial front key 'K401' thereby openingcontacts .'50 K402, thus removing the .grounded marking from conductorPUC. It'will be vrecalled that pick-up relay *440fhasv been holding overcontacts 442 and conductor "PUC; therefore" this "relay now 4releasesand opens con- 'tacts 4472; 443`and 444. y -55 {Automaticring'ing Vmay.or may not be provided and thereforethegoperation which is to followwill be `different dependingupon its provision. .First, it maybe assumedthat there is automatic ringing. After both the dial yand thedial'front'keryhave been returned to. normal, afcircuit -'is' completedfrom grounded (-1-) through .con-

tactsK-406pthe rear and'front dial keys to conductor NG-'and theautomatic ring control circuit which starts f responsive thereto. Thus,it is seen that automatic ring v"Vv'villnot begin unless'both the dialvand dial front key r|35 Shave-been returned to normal. `The automaticring controlcrcuit 'holds' over conductor HD to ,grounded (I-) atcontacts 453. 'During'this time a ground marking is ""returned 'overconductor lLK from the automatic ring circuit to .hold dial relay-460and 'off-normal relay""470 fope'rated during -the transmission oftheautomatc'ring 1.:signal. `iI-Ience, at contacts 472, relay`470'maintains refxsistasnce ybattery'on conductor ON. during transmissionof the.automaticringsignaL Following the` transmission of a.ringfsignal, grounded is removed :from vconductor :LKthusfrelea'sing'relays f4601and 470.

If automatic ringing is not provided, relays 460 and 470 releaseyresponsive to the opening of contacts 443. This in turn causes contacts461 to open thusA extinguish- "by wayofrear tip conductor RT, front tipconductor 1 FT, throughv operated contacts K211 of thering front ingdial pilot lamp 1.404, contacts 462 and 471 open the ,Y

ON1 conductor and contacts 473 further break a locking circuit to dialrelay 460. The circuit for hold relay 450 is opened at contacts 463responsive to the release of dial relay 460. Hold relay 450 remainsoperated briefly durremove the grounded marking from hold conductor H1to release dial front relay 230 having previously been held over thecircuit including contacts 463 and 454;

hold conductor H1, contacts 428, 418 and 231 to battery by way of thewinding of relay 230 which releases. When dial front relay 230 restores,idle line termination N209 is removed from across the rear cord circuit.l

Means is provided to prevent the possible association of the dialcircuit with two or more cord circuits. For example, it will be recalledthat to associatethe dial circuit with any cord circuit, it is necessaryto operate either the dial rear or dial front key thus forwarding agrounded (-1-) marking over conductor PUC.for operating relay 440 viacontacts 452. If the dial circuit is not` yet released, hold relay 450is held operated (as explained above in this section) holding Vcontacts452` open thus preventing operation of pick-up relay 440. Furthermore,relay 450 is made slow release so that contacts 452 will not recloseuntil the dialcircuit and the cord circuit have had time to becompletely disassociated.

key to conductor ST, through network' N210 and back over conductor ST1to operated contacts K213, and ring conductors FR and RR. Operation ofthe ring front key also forwards a signal for initiating ringing. v Thissignal is by way of acircuit which may ybe' tracedfrom plug P208 tocontacts `K212 and conductor SB to resistance battery B212.l

M onitorng The operator may desire to monitor the call 'at some latertime in which'c'ase she operates her monitor key K213 which forwardsafgrounded marking through contacts K214, conductor M, contacts 311 andconductor MO to monitor relay 630 which operatesand closes its contacts632`and 634, therebyV completing a circuit`from the operatorsheadsetthrough plug'P605, 'jack 1604, cable 18, contacts 632and;634,-r'epeat coil R604,- co'ntacts 613l and 615 to conductors T-1and R-l' and'contacts K215 and K216, conductors MT and MR to rear ringand tip conductors RT and RR. -At this time the operator may listenVVsince the receiver of her headset is connected by way of the sleevecontacts of plug P605 andV jack 1604; however, she may not talk sincethe talking path is open at contacts 635 and 636.

Supervision Supervisory-lamp L217 is provided for informing the Morespecifically, plug P208 is initiallyY interconnected with' jack 1209 Theoperator may disassociate her vequipment at any,

time after the dial front key is operated. lFor example,"

it has already been pointed out-how network N209 is connected if shepreviously restored talk key K202. Assume first that she has returnedthe talk key to normal and promptly thereafter operated a talk key in asecond cord circuit before theA dial circuit is disassociated from' thefirst cord circuit-for example, the diall circuit could be held brieyeither by an automatic ring circuit or by a stop dial signal whichcauses delay in dialing. There is no danger that the dial circuit may beextended to the second cord circuit because it is necessary for contacts451 to be closed before either a dial front or a dial rear relay (suchas relays 230 and 210) may be operated in a second circuit. Assuming,however, `that she did not restore her talk key previously, she willrestore it now,

thereby opening contacts K204 over which operator con-y trol relay 220has been holding. Relay 220 releases and the circuit restores to normalwith the talking path completed from rear to front cord over the circuitincluding conductors RT and RR, contacts`216 and 217, 223 and 225', 236and 238, conductors FT and FR, to plug 208.A

Anti-sidetone balance is also maintained during release of theequipment. That is, returning talk key K202 to normal opens the path tomaster relay 310 which releases. Contacts 315 open the path to relay320; however, this relay continues to hold briey during the intervaldetermined by its slow release characteristics. This delay is to preventcontacts 322 from closing a circuit to a second operator control relaybefore relay 220 has had time to release. Otherwise, there would be apossibility that two cord circuits may be lsimultaneously connectedtogether thus mingling two conversations. Contacts 314 open the pathover which operator termination relay 620 is holding to release thisrelay and shunt the talking conductors with resistance R605 therebyreturning the proper balance for anti-sidetone purposes.v

Assuming that automatic ringing is not provided, the operator may nowactuate her ring front key, signaling the called party.- Since thisfunction breaks the talking path, it is necessary to place an idle linetermination-on the rear cord to prevent howling.- The termination is i`and `a* circuit is completed for operating sleeve relay 240 over a pathwhich may be traced from grounded through. high resistance R214,the`winding of relay 240, jack 1209, plug P208, front sleeve FS, contacts221' and conductor FSI to battery by way of the windings of relays 330and 340. Relay 330 doesnot operate since'it` is marginal and thus wontrespond if high resistance R214 is in the circuit. Sleeve relay 240operates to close contacts 241.,A This sends a direct ground marking to.relay 330 which then operates becausethe closing of contacts 241- shuntsresistance R214. Following this, contacts 331 close and a circuit iscompleted for lighting supervisory lampL217 as an on-hook signal. Thecirc uit is via contacts 316 and 331, conductor'FLl, contacts 22,9,conductor FL and lamp L217.

' When subscriber C answers, contacts K245 Vare l opened by any'suitablemeans (not shown)` to remove the direct ground from conductor FS therebyreturning it to ground by wayof high resistance R214.l This causesmarginal relay 330 to release opening contacts 331`to extinguish lampL217 which the operator notes'as offhook-supervision.

On-hook supervision returns when contacts K245 close responsive to Cshanging upr at which time marginal relay 330 reoperates to closecontacts 331 for lighting lamp L217.

i plug P208 and through contacts 22,8 (both the talk key and operatorcontrol relay 220 being released) lto conductor .FL and supervisorylampL217. The high resistance of element R214 is sufficient to keeplampL217 from lighting. For on-hook supervision, low resistance groundis forwardedvia contacts K245 and '241, lthe lower winding of relay 240,over the FSKand FL leads, by way of contacts 228 thereby lightinglamp'L217.

arcane-t tion would be similar to that described above in connectionwith collect rear key. y ,A

Simultaneous connections of cord circuits 4 .Means is provided forinterlocking-.the cord circuits so that there is no chance that twoconversations will accidentally be interconnected by `means of. commonFig. 8 is useful for explainingthis feature.

while talk key K802 corresponds to `key K202. The relays of Fig. 8 areshown as having contacts which are similar to some ofthe contacts oncorresponding re-- lays in Figs. 2 and 3. Relay 810 and talk key K801are duplicates of those found in the second cord circuits. For example,the iirst cord circuit may be element 21 in Fig. 1 and the second cordcircuit may be element 20.

First let it be assumed that the' two talk keys, K801 and K802, vareoperated simultaneously.` .One circuit extends from grounded through theoperate or low resistance Winding of relay 810, `contacts K805, 832 and813 to battery B801 by way, of resistance R802.

A second similar circuit extends through the low resist-v tacts 822`which completely energizes relay 820 from .battery over its lock or highresistance winding, contacts 822, K804 and the winding of relay 840 togrounded Y is now operated, the circuit through the lowresistance Relay840 opens contacts 813. If key K801 winding of relay 810 and contactsK805 is open at contacts 832 and 813, relay 830 having *operatedV whenrelay 840 closed contacts 815.

Means is provided for preventing unduenoise when 'l talk key K802 isopened to release relaysf820 and 840.

For example, assume that both talk keys K801 and K802 are operated andthat key K802 is iopenedi -It might Y be 'possible that relay 810 wouldoperate during the interval required for relay 820 to release.

This would momentarily connect the talking conductors of the first andsecond cord circuits. While this interval is too short to hearconversation, it may be long enoughto transmit an unpleasant noise. Toforestall such` operation relay 830 is made slow-to-release, therebyholding contacts 832 open long enough to insure the .complete release ofArelay 820 before the operation of relay 810.

One nal feature is the relation between the windings of relays 820 and840.- The `buildup time during which the coils of relays 820 and 840 areenergized must be such that an inductive kickis prevented in relay 820.If this were not so, relay 820 would act as atransformer and a currentmight be induced in the low resistance winding of relay 820 during theenergization of its high resistance winding. If talk key,K,801 werethrown at that time, this inductive kick would extend over contacts K803and K805 to pull relay 810. l This feature is accomplished by increasingthe inductiveness of relay 840 which slows the buildup time in relay820. Y

However important it is to prevent the 4connection i of two cordcircuits simultaneously, there are times lwhen an operator may wish toperform va deliberate operation and exercise an option to interconnecttwo cord circuits. In this case, she will operate the talk key in onecord circuit and the monitor key of another cord circuit. The talk keyoperates master-relay 310 to forward resistance battery B301over'contacts 314 to operate relay 620. Whilethe monitor keyfinfanother,

cord circuit forwardsva grounded (el-)'- marking through:

12 contacts corresponding to K214, conductor M and contacts 312 (whichwere operated when the talk key in the first circuit pulled relay 310)to the TK conductor, thereby operating transfer relay 610. This relaytransfers conductors T-l and R-l from' repeat coil R604 to inductancecoil R603 at contacts 614 and 616. Conductors T-l and R-1 extend to themonitor, key in thesecond cord circuit, conductors MT and MR to thetalking pair of the second cord circuit. Conversation may follow betweenthe operator and/ or parties on either cord circuit. When the monitorkey is restored, ground is removed from conductor TK thereby releasingrelay 610 to return conductors T-1 and R-1 to. their normal connectionwith repeat coil R604. When the. `talk key in the second cord circuit isrestored to normal, ,the equipment releases` as explained above in thesection headed Restoration after dialing.

Busy test and out of order tone The operator may wish to make a busytestby either her front or rear cord. In either case, she touches the tipofk plug P200 or plug P208, as the case may be, to the sleeve terminalof the associated jack. If the line is busy, a battery marking isextended over the associated tip conductor from thesleeve relay ofsupervisory lamp of another cord circuit at another operator position(not shown) tocontacts 376 or 386 depending upon which cord was used.From this point, the battery marking is extended over the BT conductorto operate busy test relay 670. This relay closes contacts 671 therebycompleting a circuit to the test winding of inductance coil R603, thuscharging capacitor C604 to produce an inductive kick which the operatorhears as a click in the receiver of headset 16. If an outof-ordercondition exists,za special tone signal is on the sleeve of the testedjack and the operator lis able'to hear tone by way of capacitor C605.` v

The other cord circuit (to which reference is made -in the immediatelypreceding paragraph) is similar in detail'to that shown in Fig. 2. Sincea plug corresponding to P208 is inserted in a jack corresponding to jack1209, the battery busy marking referred to in the immediately precedingparagraph is extendedsto jack 1209V because all operator jacks are wiredin parallel.

If the talk key in the other cord circuit is thrown, the busymarkingextends through the windings of front sleeve relays corresponding to 330and 340 to aconductor similar to FSI over operated contacts 221' andconductorV FS to the sleeve of jack 1209. If the talk key in the othercord circuit corresponding to key K202 is released when the busy test ismade, the marking 4battery in the other cord circuit comes `from throughthe i .gRetard coilv R607 is used to extend a characteristic lmarkingover conductors T and R to certain trunk circuits which may require aspecial ,signal to operate a pad control relay.

Chief operator monitor has taken position.

Itmight be recalled that Vwhen theoperator tookposis 'amil-gcc4 coilR604 whereby .the-chief'ioperatot may: [listen-2y Min #son uthe:operators iconversation. wt;- c'ontactsf'637 a .circuit is'iclosed: foralighting af=supervision\rlamp';f(not shown) f atzrthenchiefnoperatorsdesk: apprisin'g.fdierifoffttheafact ithat-the operator is monitoring-:ac'all.

-fitoring the'"call;ahowever,she is 'connected-with a:subsscriberbecause sa;talk"key is thrown in .-oneiof the :cord'.icircuitsf :In Sthis case, monitor relayx' is Jnotroperated andtherefore the chief operator may listen in-'over the Isglrrthieirtendingoverv conductors. CRa'andCT,Ycontactsi" cover notfonlynhespecific-embodimentLshown in theY accompanying drawings. vvand4vdescribed.- 4above, but also these claims should cover thosemodiiications which may be v"apparent to person 'skilled 'intl-.refaitl. In a telephone system, an operators position com-ifA prising a cordcircuit including a front and a rear sleeve conductor, an operatorsheadset and an operators circuit, a position circuit accessible to saidcord circuit, said operators circuit comprising a talking path includinga two winding induction coil for connecting said headset with saidposition circuit, means for balancing said induction coil to avoidsidetone in said operators headset, control means for switching saidanti-sidetone balancing means into and out of said talking path andmeans for operating said control means depending upon the markingextended over at least one of said sleeve conductors to said positioncircuit.

2. The device of claim 1 in which said cordcircuit comprises a frontcircuit and a rear circuit either or both of which may be included insaid talking path, a first and a second switching means, means foroperating said iirst switching means via said rear sleeve conductor whensaid rear circuit is connected to an associated circuit, means foroperating said second switching means via said front sleeve conductorwhen said front circuit is connected with an associated circuit, andother circuit means effective upon the operation of either said first orsaid second switching means for operating said control means, saidanti-sidetone balancing means consisting of a resistor.

3. The device of claim 2 and contact means for disconnecting saidtalking path from either said front or said rear circuit, a terminatingnetwork and means for connecting said terminating network to that one ofsaid circuits from which the talking path is disconnected.

4. The device of claim 3 in which said contact means includes means forcausing said control means to switch said anti-sidetone balance meansinto said talking path when one of said switching means, correspondingto that one of said circuits to which said talkingpath is 70 stillconnected, is not operated. Y

5. A toll board comprising a plurality of cord circuits and othercircuits common thereto, means for connecting one of said cord circuitswith said common circuits, interlock means for preventing thesimultaneous 'i110 1; operated byisaidsmaster srelay '72?14'a;:minnectcmv ofa plurality tir-:saidfnordacirexts wthusaid lrcommonvfcircuits; .zsaidminterloclcumeans -ncomprisi'ng= la -"lrelay.:infeach-s oft-said -x-:or'd f-cireuits'i and .anmasternrelay ginrsaidcommoncircuits,:meansffor bperatin'gfsadzmaster i5 relay when only oneof said cord circuits is connected e withirsairlycommon-:circuit-,andsfcireuitximeans controlled l'by the"operatiom onsairl1..niaster :re'layl 'for-i disablingr'said ,irela'ysi in ieachzfofsaid `ycol-clicircuitsz'eircept` fonathewre- 'layirrsaid'oneivcordicircuitmdm r, `-.';AA i6.-v The''devi'ce 4c'vffclairn` 5in which''each fof-:isaidrcord 'circuit .relaysinclud'esf antoperategmvinding; mearisyfor ,'connec'ting'f.A ^said rioperatef.,iwindings; inf.L1 parallel and `for .1 zc'onnectinigasaidparallelecircuits infrsericsriwith 'ai szontact con :saidfniastetz'zrelayA I,and *means sfor Iindividually @losing l5 -feachof/said 1 parallel i circuit'syeaclr4 of .saidsoperatev `:windgings;being oft such lowfresistance Vthat-none of said :relays .will openate'yif ymore tl1xaur-onetof. said iparallelfacircuits.iaresclosed-simultaneously.: w A 7.;;Thesdevice of claim and means/aferhalf-operating fone of saidzrelays Yoiver iitsaoperate vwinding, when'l,only

.ethatxone,of-fsaidpparailel circuits with :zwhich it rislas- .sociatedis I ,'elosed;f contact rim'eans' ':sfcontrolled-` by @fsaidhalf-operated onelrelaygaflookwinding: bns'said ione.- relay, meansincludingus'aidcontact means.f'for;connecting: said `dock windinginffseries` with said-:master .frelayc whereby fsaid one :Irelayaiocksand rsaidvmasteri :,-relay operates -to 'z 7op'err :its rsaid contactrth'ereby openingffall Iof ./said; parallelwcirouiteftorallofrsaidiroperatefvindings. 1.

rllheffdevicezofzolaim andi'iaaftimeelayffdevice rothercontact :meanscon- "zirtzxlledwbylv 'saidntimeiidelafy sdevice'fand :includelilin::the aidfseries":cireuitextendingfmm:saidrparallel circuits yto sid:fcontacnfonasaidvmaster ,relaygxmeans uforifopening:saidseries'rcirctt thereby :releasingfsaidtmastermelayaandopetl'ingvitsrcontacnmennsficompletedl =b,y r'thef rclcasepf said masterrelay for operating said time ldelay device thereby measuring a briefinterval of time, said other ycontacts controlled by said time measuringdevice being held open during said brief interval of time and closed 40thereafter whereby after said interval said series circuit is againprepared to complete one of said parallel paths.

9. An operators toll board including a plurality of telephonelinesterminated thereat, a plurality of cord circuits each of which may bemade individual to any of said lines, other circuits common to saidplurality of cord circuits, first means operated to a first position forrendering any of said Acord circuits individual to at least one of saidcommon circuits and holding means in said one common circuit formaintaining said individual connection between it and said cord circuitindependently of said first means, whereby said operator may return saidiirst means from said first position at any time without releasing saidindividual connection.

10. The device of claim 9 in which said individual cord circuit includesmeans for completing a' circuit vfor the transmission of control signalsto an automatic switch train.

11. The device of claim 10 in Vwhich each of said cord circuits includesa tip and a ring conductor, circuit means for vconnecting said signaltransmission means to transmit said switch directing signals over saidring conductor and other circuit means for connecting said one commoncircuit to transmit supervisory signals over said tip conductor. a

l2. A11 operators toll board comprising a plurality of cord circuits anda dial circuit common thereto, means for individually connecting saiddial circuit with one of said cord circuits, holdingmeans forI lockingsaid dial circuit in said connection and circuit means controlled bysaid locking for preventing the simultaneous connection of two or moreof said cord circuits with said dial circuits.

13. The device of claim 12 in which said holdingv means comprises a slowrelease relay, a dial including olfnormal springs and a contactgdevice,circuit means ineluding said-.dialfoi-normal springs and said-.contactdevice for lockingsaidslowirelease `relay .operated and means forreleasing said relay only when both said offnormal' springs and `saidcontact-device are in normal position.4 A

14. In a telephone system, an-operatortoll board comprising apluralityof-cord circuits, a position circuit and vnxittingfasupervisoryl signal to said position for appris- -ing saidchiefoperatorvofthe. fact that the toll `board operator has taken position,means. at saidtoll -board .for monitoringany of-said cord I-circuits,lrneans forltransmitting a supervisorylsignalto said-position forapprising said chief operator-of the factfthat the toll operatoris'monitoring a call and means whereby said chief operator may beoperatively connected'to said'tollV board at any time for observing theconduct of the toll operator.

15. In a telephone4 system, a toll switchboard com-A prising a`plurality ofcord circuits, *common circuits,

` means in each of saidcord circuits comprising a talk ykey t and a twowinding operatorcontrolrelay for connecting one 'cord circuit to vsaidcommon circuit, one offsaid two windings being'of a high resistance `andthe other -of said two windings beingtof a low resistance, a given vparticular cord circuit for connecting `said'low resistance winding ofone of said operator -control relays in said -particular'cord circuit tosaid given potential to operate said operator control relay, said lowresistance winding being of such value that two operator control relaysmay so Y not be operated simultaneously, a master relay, meansresponsive to saidoperation of saidv one operator controlY relay forconnecting said high resistance winding of said one operator controlrelay in series with said master relay whereby. said one operatorcontrolrelay locks in an operatedposition and said masterrelay operates,and means responsive to operation ofsaid master [relay for .opening saidcircuit from said given potential tosaid -low resistance windings Y'ofsaidpoperator control relays-in each ofz said cord circuits. I

16. The device of claim l5i and a slow release slave relay, meansresponsive to operation'of said master .relay for operating said slaverelay, meansresponsive to operation of said slave relay for opening aI,second point in said circuit fromy said given potential to said lowresistance windings, and means responsive to restoration of said talk`key for opening said circuit connecting said high resistance lwindingand said master'relay in series. I v

.17. The telephone system of claim 15 wherein the relative inductivereactances of said high resistancewinding and the winding of saidAmaster relay is such'that the inductiveness of said masterI relaywinding is of suflcient magnitude to slow the build-up time'ofr theinduction eld of said high resistance winding i of said operator controlrelay thereby preventing aninductive kick through the lowresistancetwinding of said operator control relay. v

References Cited in the leof this patent i n UNITED STATES YPATENTSNelson June `2.75,4 1914219 Saul A. iJune 8,19%7

